The invention resides in a laser machining apparatus and a method for the manufacture of a tool, especially a rotationally symmetrical tool from a blank. The blank is to be provided with one or several chip grooves, cutting edges, cutting faces and end flanks. The blank may include also several material layers or several joined elements as for example a hard metal shaft and a diamond tool insert.
For the machining of such blanks various ablation methods are known, for example grinding. The grinding of very hard materials, such as polycrystalline diamonds (PKD) of CVD diamonds (Chemical Vapor Deposition) is limited in technical as well as economical respect. Particularly with very small dimensions only certain chip groove geometrics can be manufactured by grinding. In addition, the force effects on the blank are very large and may lead to undesired deformation. The laser ablation using short-pulsed lasers offers new possibilities of machining these materials economically in the manufacture of, for example, tools.
The manufacture of high-quality tools however is problematic. In the current state of the art, laser systems are known which scan the tool contour with the aid of a laser scanner wherein the blank is stationary with respect to the scanner. These laser scanners operate at very high scanning speeds during scanning of the blank by the individual laser beam impulses. However, the achievable accuracy does not comply with today's requirements. In addition, the surfaces and edges formed in the process deviate from a straight course and have an uneven jagged course.
Furthermore, laser machining apparatus are known where the laser is moved along machine axes relative to the blank. Although a higher accuracy and a higher quality of the surfaces and edges formed on the blank can be obtained in this way, the ablation rates which can be achieved thereby are low. This is because the dynamics and the speed of the machines axis are limited. For increasing the dynamics of the machine axes, large efforts and expenses are necessary which make the laser machining apparatus very expensive.
A method and apparatus for laser machining a blank are known for example from DE 299 08 385 UI. The apparatus includes a laser for generating laser impulses. Via a drive unit the laser and/or the tool blank holder are moved in the direction of and transverse to the optical axis of the laser. The laser beam is moved in the process along several adjacent or overlapping lines over the whole width of the surface to be removed. The material is therefore removed at the impinge locations of the laser impulses point-by-point. In order to obtain a continuous material ablation, the impinge locations overlap by 5-25%. With pulsed lasers of high frequency correspondingly large advancing speeds are herefor necessary. As already noted, the ablation rate in this procedure is low and machining time is correspondingly large.
In WO 2006/038017 A2, two different embodiments of a laser machining apparatus are described. In the first embodiment with the aid of a laser scanner a pulse area of several adjacent impingement locations for the laser impulses is formed. The material ablation occurs at the impingement locations of the laser impulses within the pulse area. In a second embodiment no real material ablation is effected, but the blank is severed. First a passage is drilled through the blank. After completion of the passage, an advance movement is initiated for cutting the blank in one sweep. This corresponds to the initially described variants of laser machining.
DE 10 2007 012 815 AI discloses a method wherein the impingement locations of the laser beam impulses are placed by means of a scanner along a grid pattern. Superimposed thereon, one-or two dimensional relative movement between the grid pattern and the impingement location can be performed. This superimposed relative movement should be faster than the path movement of the laser impulses by the scanner. How such a fast superimposed movement could be achieved is not disclosed. Known machine axes could not possibly provide therefor.
Based on these known methods and apparatus, the object of the invention is viewed in providing an improved method and laser machining apparatus for the manufacture of tools.